1. Field of the Invention
The present invention relates generally to ultrasonic imaging and, more particularly, to creating multiple planar ultrasonic images of a volumetric region of the body in real-time. In addition, the present invention relates to a method and system for addressing temporal artifacts in a three-dimensional (3D) ultrasound image of a volume.
2. Description of the Prior Art
In three dimensional (3D) ultrasound imaging, a volume, such as the volume of a heart, is scanned with ultrasound beams and the resultant echoes are used to form an image of the anatomy associated with the volume. In known 3D ultrasound imaging systems, making an image of a significant volume requires a significant amount of time for transmittal of the ultrasound beams necessary to spatially sample the volume adequately. Consequently, the time required to make one volumetric image is overly time consuming, which results in reducing the frame rate of a real time display that is used to display the ultrasound images. In addition, such known prior art systems require a substantial amounts of processing power for processing a volumetric image.
Current 3D ultrasound systems typically display 3D images using either a multiplicity of separate scan planes, or a 3D rendered volume. In either case, the acoustic scan lines, which provide the source of the image data, are arranged in raster patterns. The acoustic scan lines are swept through one dimension to form slices, and slices are swept through an orthogonal dimension to form the volume. An example of such a prior art system is the Volumetric 3D ultrasound scanner. In other known 3D ultrasound systems in which 3D images are displayed by means of multiple planes taken from a volume of interest, only the scan lines from the planes that are displayed may be scanned, but still, the lines of each plane (or slice) are scanned in a single raster sweep across the slice, and the slices are scanned individually.
For example, rather than displaying an entire 3D volume, one display approach, discussed above, is to select planes in a volume for display. Examples of such systems are illustratively shown in U.S. Pat. No. 5,546,807 which is hereby incorporated herein by reference in its entirety. Examples of systems that display two planes are illustratively shown in U.S. Pat. No. 6,241,675, which is hereby incorporated herein by reference in its entirety.
However, if only selected planes of a volume are of interest, the time taken in known systems to scan the other parts of the volume is of very little benefit to the displayed image. Examples of systems in which only the planes that are to be displayed are scanned are illustratively shown in U.S. Pat. No. 6,276,211, which is hereby incorporated herein by reference in its entirety.
Nevertheless, there are features of these prior art systems that are presently unsatisfactory. The frame rates for volume scans, even for the simpler multi-plane 3D formats, are much lower than for single-plane scans typical of today""s systems. This is because scanning a volume requires roughly the square of the number of scan lines required for a planar scan. Accordingly, there is a greater time delay between scan lines at the beginning of a frame than those at the end of a frame. That delay causes significant temporal artifacts, whereby the anatomy presented in a single display frame appears geometrically distorted or discontinuous due to the movement of the tissue structures from the time of the first scan line in the frame up to the last scan line in the frame. The phenomenon is called xe2x80x9ctemporal discordancexe2x80x9d or xe2x80x9ctemporal artifact.xe2x80x9d xe2x80x9cTemporal discordancexe2x80x9d occurs because the scan lines of a frame are generated over an extended time window, yet the resulting frame is rendered on the display very quickly, presenting the view as though all the parts of the anatomy were measured simultaneously. xe2x80x9cTemporal discordancexe2x80x9d is especially apparent when reviewing a series of frames one at a time, where the user can examine and compare the tissue structures displayed in adjacent scan planes that are supposed to be simultaneous.
Accordingly, it is clear that there exists a need for a method and a system for addressing temporal discordance as described above.
In accordance with the principles of the present invention, method and apparatus are described for creating and displaying multiple planar images of a volumetric region of the body. In one aspect of the invention, two real-time image planes are acquired and displayed in what is referred to herein as a xe2x80x9cbiplanexe2x80x9d display format. The two planes of the biplane display can be controlled in two control modes, one in which one image plane is tilted relative to the other, and another in which one image plane is rotated relative to the other. In another aspect of the invention, an icon is displayed concurrently with the biplane images to inform the clinician as to the relative orientation of the two image planes.
In accordance with another embodiment of the present invention a method of minimizing temporal artifacts in an ultrasound image of a volume is provided. The method includes the steps of selecting a plurality of planes of the volume, scanning a portion of the volume defined by the plurality of planes by alternating between the plurality of planes in a time interleaved manner with an array transducer, generating a three dimensional data set based on the scanning and displaying views of the plurality of planes based on the three dimensional data set.
In accordance with yet another embodiment of the present invention, a method for preventing occurrences of temporal artifacts in an ultrasound imaging display is provided. The method includes the steps of determining a fast moving region of interest, scanning the region of interest with a higher transmit beam density than other regions, performing a scan conversion, and displaying an ultrasound image.
Additional summary information is provided below.